It seems to have so far escaped OSNews' notice (if the top few hits for a site-search for 'Steam' is any indication) that Steam for Linux is now in Open Beta; you can get the Linux steam client from steampowered.com. So far, they appear to only be making an Ubuntu .deb available, and the client will require closed-source GPU drivers in order to work.

Tried the Steam beta using Ubuntu 12.10 32-bit using Bumblebee with optirun and primusrun. Serious Sam 3 BFE runs but the frame rates are abysmal making the game essentially unplayable. I wish nvidia would release even an alpha version of some Optimus drivers. This situation is just ridiculous. My video chipset is Intel HD4000/GTX 670M and I'm using the experimental 310 drivers for the nvidia side of the house. My screen res is 1600x900.

The Unigine Heaven benchmarks are crappy too. I get roughly 9-12 fps. The Tropics benchmark is somewhat better at 15-22 fps. Is anyone out there getting any better frame rates than those I've posted?